Dry ice snow flakes appear to fly on planet Mars

Mars ain’t the kind of place to raise your kids/In fact it’s cold as hell. - Elton John

Via NASA: “This map shows the distribution of small-grain carbon-dioxide ice deposits formed by snowfall over the south polar cap of Mars. It is based on infrared measurements by the Mars Climate Sounder instrument on the Mars Reconnaissance Orbiter.”
(NASA )

The Mars Rover recently recorded a temperature of -132 degrees, an intensity of cold difficult to comprehend. Yet on Mars, in­cred­ibly, that’s too warm for it to snow. It needs to be minus 193 degrees, the temperature required for carbon dioxide to freeze and dry ice to form.

New NASA research provides convincing evidence that there are snowflakes in the clouds on Mars and that they find their way to the ground.

“We firmly establish the clouds are composed of carbon dioxide -- flakes of Martian air -- and they are thick enough to result in snowfall accumulation at the surface,” says Paul Hayne, lead author of a new study on Martian snow being published in the Journal of Geophysical Research (JGR).

NASA says Mars is the only planet in the solar system privy to accumulation of this kind of snow. But it’s not exactly known how the snow gets from clouds to the ground.

“It is unclear whether [the deposition] occurs as snow or by freezing out at ground level as frost,” NASA reports.

But views into the clouds and particle data offered by the Mars Climate Sounder (aboard the Mars Reconnaissance Orbiter) suggest snowfall the authors say.

“One line of evidence for snow is that the carbon-dioxide ice particles in the clouds are large enough to fall to the ground during the lifespan of the clouds,” said NASA’s David Kass, study co-author. “Another comes from observations when the instrument is pointed toward the horizon, instead of down at the surface. The infrared spectra signature of the clouds viewed from this angle is clearly carbon-dioxide ice particles and they extend to the surface. By observing this way, the Mars Climate Sounder is able to distinguish the particles in the atmosphere from the dry ice on the surface.”

NASA says the most “vigorous” snowfall occurs on Mars’ south polar residual ice cap and it sticks year-round due to the frigid temperatures there.

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